GAUI EP 100 SE/Pro RC helicopter: Hunting down the gremlins

Main blades / shaft

• Check main blade balance
• Replace the 2x10 screws that attach the blade holders to the head
.
Those screws get easily bent, even if the blades didn't take any damage.
My most frequent issue with the SE was the screws coming loose during flight, then it starts to wobble. A drop of blue Loctite keeps them in place (SE only). Don't overtighten, friction is bad.

• Check blade tracking
Seen from the front or side, both blades need to spin in the same plane. If not, adjust push rods.

• Check / replace the main shaft. Roll on a glass surface. If needed, it can be bent back to "good enough" shape without any tools.
• Make sure there is no or only little friction in the rotor head mechanics. This may take some hours of flight to break in the ball links. See below
• Check flybar balance by taking off the ball joints.
Hint: use fresh blades for setting up. Blades that were patched up may be good for flying, but may also invite more "gremlins".

Tail

• Check that the tail belt is not flipped
Reportedly, it is a good idea to lubricate the belt (oil or silicon). If the belt still flips, it needs to be replaced.

• Check tail belt tension (no slack but not tighter)
• Balance the tail blades CAREFULLY
The tail rotor may be a quarter the size of the main rotor, but it spins four times faster as well. Watch it when it runs, and do this with main blades off (because main blade vibrations appear also at the tail, this can be confusing). A badly balanced tail assembly turns into a blur at speed, for example half a centimeter. If it's balanced, it remains more or less "in focus".
Is the tail assembly at a proper 90 degree angle? (no big deal if not, but easy to fix)

• Does the tail fin resonate at any headspeed? A possible solution can be found on the “setup tips” page.

EP 100 SE only

• Glue the "aileron" servo mount on the left to the main frame, and use some wire on the back end to keep it in place
A loose servo mount is nasty, because you may not notice it immediately.

• Some rubber "washers" between rudder servo and frame (optional, small improvement)

Headspeed

Rotor head

• Too little tension, and the heli will swing shortly, when recovering from rapid moves
• Too much tension, and the heli will swing (wobble) continuously in hovering

Other

• Isolate the gyro from vibrations, see my other page
• check that all servos are still PERFECTLY glitch free
Move the stick as slowly as you can. If the servo seems to get stuck and "catches up" later, it's broken. Same if it twitches, hums at the endpoints or lacks power (that happens when the servo overheated, and the magnets lost their magnetization)

• Spin up the heli without blades, and get a feeling for the vibrations. With blades it should not feel very different
• And one thing more, not as obvious as it sounds: Take your time and check all the parts
Once, not too long ago, I had it flying with one lever disconnected in the rotor head, one screw had dropped out. Stability suffered, and for a long time I thought it was me who is having a bad day.

Last but not least

Lower: tail blade holder bearing. Upper: two rotorhead bearings

Comments? Questions?